From phpmyadmin you cannot send mails ...
You can extract the emails in phpmyadmin with this sql query :
PHP Code:
SELECT `email` FROM `users` WHERE 1
My guess is that you have just a database and you want to send spams to others to increase your user number, but I may be mistaken.......
Otherwise, if you had your own database, you could send mass mail through the tracker mailer ....
Good luck!